The present invention is directed, in general, to switching devices and, more specifically, to an ATM switch that uses measured quality of service data from other ATM switches to route data cells.
Information systems have evolved from centralized mainframe computer systems supporting a large number of users to distributed computer systems based on local area network (LAN) architectures. As the cost-to-processing-power ratios for desktop PCs and network servers have dropped precipitously, LAN systems have proved to be highly cost effective. As a result, the number of LANs and LAN-based applications has exploded.
The increased popularity of LANs has led, in turn, to the interconnection of remote LANs, computers, and other equipment into wide area networks (WANs) in order to make more resources available to users. However, a LAN backbone can transmit data between users at high bandwidth rates for only relatively short distances. In order to interconnect devices across large distances, different communication protocols have been developed. The increased popularity of LANs has also led to an increase in the number of applications requiring very high-speed data transmission. Applications such as video conferencing require a large amount of bandwidth to transfer data and are relatively intolerant of switching delays.
The need for higher speed communication protocols that are less susceptible to switching delays has led to the development of the asynchronous transfer mode (ATM) telecommunications standard. ATM was originally intended as a service for the broadband public telephone network. Although designed primarily for the high-speed transfer of video and multimedia information, the most popular applications for ATM so far have been data transmission. ATM is widely used as the backbone of large business networks and in wide area networks.
ATM provides speeds from 50 Mbps up to 10 Gbps using fast packet switching technology for high performance. ATM uses small fixed-size packets, called xe2x80x9ccellsxe2x80x9d. A cell is a 53-byte packet comprising 5 bytes of header/descriptor information and a 48-byte payload of voice, data or video traffic. The header information contains routing tags and/or multi-cast group numbers that are used to configure switches in the ATM network path to deliver the cells to the final destination.
Many packet switching architectures have been developed for implementation in ATM networks. One such architecture, known as multistage interconnection network (MIN), comprises a switching fabric that routes packets received from one of N input ports to one or more of N output ports. The multistage interconnection network comprises groups of switching elements arranged in multiple stages. Each stage uses one or more bits in the packet (or cell) header to select the output to which the input packet is routed. This type of routing is known as xe2x80x9cself-routingxe2x80x9d.
Customer demand for additional bandwidth beyond the capabilities of frame relay and other technologies has led the majority of telecommunication carriers to offer ATM service to customers. ATM service has low latency and predictable throughput due to the small cell size and tremendous speed of ATM technology. This makes ATM service desirable in networks that handle a mixture of data types, such as voice and video. ATM applications include conventional data transfers, imaging, full-motion video, and multimedia.
One important feature of ATM service is the ability to establish specific Quality of Service (QoS) levels to meet each customer""s needs. The QoS requirement is critical in delay-sensitive applications, such as real-time audio, real-time video, and, to a lesser extent, Internet telephony. In broadband connections, the QoS of an end-to-end connection is very important, especially for constant bit rate (CBR) and real-time variable bit rate (RT-VBR) traffic connections.
The path that an ATM cell takes through an ATM network may be determined by several different well-known route selection algorithms. Generally, these prior art route selection algorithms are based on xe2x80x9cstaticxe2x80x9d routing tables and do not take into account present resource (e.g., switch) congestion or certain critical QoS factors. In many cases, the route taken through the entire ATM network, or at least a significant portion of it, is selected by the source switch without giving consideration to dynamic traffic congestion levels and QoS conditions at intermediate switches along the path.
Protocols exist in the prior art that verify whether a connection already established by a route selection algorithm in a switch satisfies the end users QoS requirements. If the established connection does not meet the end-user""s needs, the protocol causes the switch to terminate the connection. The route selection algorithm must then select another route and the QoS requirements must be re-verified. The prior art algorithms do not attempt to use QoS data/statistics in the initial selection of a route through an ATM network.
There is therefore a need in the art for an improved ATM switch architecture capable of selecting an optimal route through an ATM network on the first connection attempt. In particular, there is a need for an improved ATM switch architecture that uses relevant QoS data to select an optimal route through an ATM network on the first connection attempt. There is a still further need for an improved ATM switch architecture that uses the most recent traffic congestion and QoS data to select an optimal route through an ATM network on the first connection attempt.
To address the above-discussed deficiencies of the prior art, it is a primary object of the present invention to improve the call/connection setup time of a switched virtual circuit (SVC) or a permanent virtual circuit (PVC) in an ATM network by using the most recent congestion data and quality of service (QoS) data within the ATM switches located in the ATM network. It is another object of the present invention to provide a deterministic method for selecting a route for a SVC or PVC in an ATM network that will satisfy the QoS requirements of an end user.
These objectives are met by means of a special purpose connection between adjoining ATM switches in an ATM network or between an ATM switch and a service control point (SCP) in an ATM network. This special purpose connection comprises a virtual channel circuit (VCC) connection that is established between adjoining ATM switches, or between an ATM switch and an SCP. The VCC connection is used to transfer to a recipient ATM switch selected traffic congestion data and selected QoS data about other ATM switches, such as, for example, the sending ATM switch.
Accordingly, in an advantageous embodiment of the present invention, there is provided, for use in a switching network, an asynchronous transfer mode (ATM) switch comprising: 1) a plurality of input ports capable of receiving ATM cells from user nodes and from adjoining ATM switches in the switching network; 2) a plurality of output ports capable of sending ATM cells to user nodes and to the adjoining ATM switches in the switching network; 3) a database capable of storing at least one of quality of service (QoS) data and congestion level data received from the adjoining ATM switches; and 4) a route selection controller capable of transferring a selected received ATM cell from a first of the input ports to a selected one of the output ports in response to the QoS data stored in the database.
In one embodiment of the present invention, at least one of the received QoS data and congestion level data is associated with a specific port on one of the adjoining ATM switches.
In another embodiment of the present invention, the ATM switch is capable of detecting QoS cells containing QoS data and congestion level data received from the adjoining ATM switches.
In still another embodiment of the present invention, the ATM switch further comprises a monitoring device for determining at least one of QoS data and congestion level data associated with the ATM switch.
In a further embodiment of the present invention, the ATM switch creates a QoS cell containing at least one of the QoS data and the congestion level data determined by the monitoring device.
In yet another embodiment of the present invention, the ATM switch transfers the QoS cell to at least one of the adjoining switches.
In a still further embodiment of the present invention, the ATM switch further comprises a switch fabric capable of transferring received ATM cells from the input ports to the output ports.
According to yet another embodiment of the present invention, the route selection controller selects the selected output if at least one of the stored QoS data and the congestion level data associated with a specific remote port on an adjoining ATM switch coupled to the selected output port compares favorably with a QoS requirement associated with the selected received ATM cell.
The foregoing has outlined rather broadly the features and technical advantages of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features and advantages of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they may readily use the conception and the specific embodiment disclosed as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form.
Before undertaking the DETAILED DESCRIPTION, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms xe2x80x9cincludexe2x80x9d and xe2x80x9ccomprise,xe2x80x9d as well as derivatives thereof, mean inclusion without limitation; the term xe2x80x9cor,xe2x80x9d is inclusive, meaning and/or; the phrases xe2x80x9cassociated withxe2x80x9d and xe2x80x9cassociated therewith,xe2x80x9d as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, be a property of, be bound to or with, have, have a property of, or the like; and the term xe2x80x9ccontrollerxe2x80x9d means any device, system or part thereof that controls at least one operation, such a device may be implemented in hardware, firmware or software, or some combination of at least two of the same. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases.